Method of making compression fitting

ABSTRACT

THE DISCLOSURE PERTAINS TO A COMPRESSION FITTING FOR CONNECTING CONDUIT TO OUTLE BOXES AND THE LIKE IN WHICH THE BODY MEMBER IS MADE BY A SERIES OF PRESS FORMING OPERATIONS ON A TUBULAR BLANK TO DEFINE A CENTRAL UPSET PORTION HAVING A HEX CONFIGURATION, AND ROLL FORMED THREADED END PORTIONS OF DIFFERENT EXTERNAL DIAMETERS IN WHICH THE DIAMETER OF THE TUBULAR BLANK IS EQUIVALENT TO THE PITCH DIAMETER OF THE LARGE END OF THE COMPLETED BODY MEMBER, AND AN INDENTATION IS ROLLED INTO THE BLANK ADJACENT ITS SMALLER END TO DEFINE THE MAXIMUM THROAT SIZE OF THE FITTING AND STOP FOR THE CONDUIT WHEN RECEIVED IN THE BODY MEMBER LARGER END. IN MAKING THE BODY MEMBER, THE BLANK IS FORMED BY SEVERING SAME FROM THE TUBING TO INCLUDE THE INDENTATION LOCATED ADJACENT ONE END OF SAME, THE ENDS OF THE BLANK ARE DEBURRED, THE SAID ONE END OF THE BLANK IS NECKED DOWN TO APPROXIMATELY THE INDENTATION, THE BLANK IS UPSET INTERMEDIATE ITS ENDS TO DEFINE THE HEX CONFIGURATION, AND WHEN THE THREADS ARE ROLLED INTO THE BLANK ENDS, AFTER WHICH THE BODY MEMBER IS SUITABLY COATED. THE REDUCED END OF THE BODY MEMBER RECEIVES A CONVENTIONAL BOX ENGAGING LOCK NUT WHILE THE LARGER BODY MEMBER END IS EQUIPPED WITH A CLAMP NUT AND COOPERATING GLAND FOR FIXING THE CONDUIT TO THE FITTING. ALSO DISCLOSED IS A SPECIAL DIE ARRANGEMENT FOR NECKING DOWN AND UPSETTING THE FITTING BODY MEMBER.

Nov. 2, 1971 Fild Dec. 4, 1968- N. H. RUDOLPH ETAL 3,616,522

METHOD OF MAKING COMPRESSION FITTING 4 Sheets-Sheet 1 w wxmw ATTO RNEYSNov. 2, 1971 RUDQLPH ETAL 3,616,522

METHOD OF MAKING COMPRESSION FITTING Filed Dec. 4, 1968 4Sheets-Sheet zF168 INVENTORS NATHAN Hv RUDOLPH RONALD G. BOYD AT TORN EYS METHOD OFMAKING COMPRESSION FITTING Filed Dec 4. 1968 4 Sheets-Sheet 3 FIG9 I Iuse) \86 \64 i I 2 I70 290 148 62 I I \94 M I 50 Q I I I 3) FIG.

IO FISH IN NTORS NA N UDOLPH RON D G. BOYD ATTORNEYS Nov. 2., 1971 N. H.RUDOLPH ET AL 55 METHOD OF MAKING COMPRESSION FITTING 4 Sheets-Sheet 4.

Filed Dec. 4, 1968 INVENTORS NATHAN H. RUDOLPH RONALD G. BOYD ATTORNEYSBY W United States Patent US. Cl. 29-458 6 Claims ABSTRACT OF THEDISCLOSURE The disclosure pertains to a compression fitting forconnecting conduit to outlet boxes and the like in which the body memberis made by a series of press forming operations on a tubular blank todefine a central upset portion having a hex configuration, and rollformed threaded end portions of different external diameters in whichthe diameter of the tubular blank is equivalent to the pitch diameter ofthe large end of the completed body member, and an indentation is rolledinto the blank adjacent its smaller end to define the maximum throatsize of the fitting and a stop for the conduit when received in the bodymember larger end. In making the body member, the blank is formed bysevering same from the tubing to include the indentation locatedadjacent one end of same, the ends of the blank are deburred, the saidone end of the blank is necked down to approximately the indentation,the blank is upset intermediate its ends to define the hexconfiguration, and then the threads are rolled into the blank ends,after which the body member is suitably coated. The reduced end of thebody member receives a conventional box engaging lock nut while thelarger body member end is equipped with a clamp nut and cooperatinggland for fixing the conduit to the fitting. Also disclosed is a specialdie arrangement for necking down and upsetting the fitting body member.

This invention relates to compression fittings for connecting EMT orthin wall conduit to outlet boxes and the like, and more particularly,to a compression fitting in which the body member is formed from tubestock, and a method of making same.

Heretofore, compression fitting body members have been formed byemploying die casting techniques or by deep drawing a flat blank, whichinvolve sophisticated tooling, expert handling, and significant materialwastage.

A principal object of this invention is to provide a method of makingcompression fittings from tube stock which substantially eliminateswastage and permits the use of simplified tooling.

Another principal object of the invention is to provide a compressionfitting arrangement in which the body member is fabricated from tubestock by simplified and labor saving procedures.

Other objects of the invention are to provide a method of making thebody member of compression fittings that is composed of simplified pressforming steps which involve no significant material wastage, to providea method of making compression fittings that is readily adapted foreconomical mass production purposes, to provide a die arrangement thatis especially adapted for press forming the fitting body member, and toprovide a compression fitting that is economical of manufacture,convenient to apply, and long lived in use.

Other objects, uses, and advantages will be obvious or become apparentfrom a consideration of the following detailed description and theapplication drawings in which like reference numerals indicate likeparts throughout the several views.

In the drawings:

3,616,522 Patented Nov. 2., 1971 ice FIG. 1 is a plan-view of an outletbox having the compression fitting of this invention and a length of EMTapplied thereto for the purpose of securing EMT (or thin walled conduit)to the box;

FIG. 2 is an exploded view illustrating the part-s of the fitting, thebox wall to which the same is clamped, and the end of the conduit thatis applied thereto;

FIG. 3 is a sectional view through the fitting as applied to the conduitend, with the box wall and lock nut omitted;

FIG. 4 diagrammatically illustrates the initial blank forming operationsin which the tube stock from which the fitting body member blank isformed is processed to define the blank;

FIG. 5 is a side elevational view of the blank as formed by performingthe steps illustrated by FIG. 4;

FIG. 6 is a sectional view of the blank shown in FIG. 5, on a somewhatenlarged scale;

FIG. 7 diagrammatically illustrates the next step of the method in whichthe ends of the blank are deburred,

with the blank being shown in section and the deburring tools beingshown in elevation;

FIG. 8 is a fragmental view of one end of the fitting showing thechamfered inner edge surface that is formed of the step of FIG. 7;

FIG. 9 is a vertical sectional view, partially in elevation,illustrating the die arrangement that is employed to neck down one endof the blank and upset the mid portion of the blank to define the hexshaped mid portion of same;

FIGS. 10 and 11 illustrate the shaping that the blank takes in goingthrough the two stage shaping procedure performed by the die arrangementof FIG. 9; and

FIG. 12 diagrammatically illustrates a dial feed die arrangement inwhich the die structure of FIG. 9 is incorporated.

However, it is to be understood that the specific drawing illustrationsprovided are supplied primarily to comply with the requirements of thePatent Code, and that the invention may have other embodiments which areintended to be covered by the appended claims.

GENERAL DESCRIPTION Reference numeral 10 of FIG. 1 generally indicatesthe compression fitting of this invention applied to an outlet box 12for the purpose of securing to same conduit 14.

The box 12 is entirely conventional in nature and is intended torepresent any standard form of outlet box, switch box, and otherstructures of this character to which the fitting 10 can be applied. Box12 includes bottom wall 16 and side walls 18 formed with the familiarknock outs 20, each of which, when removed, defines box opening 22 (FIG.2) to which the fitting 10 is applied.

The fitting 10 generally comprises a tubular body member 24- definingthreaded end portions 26 and 28 separated by a hex shaped median portion30 defining a rounded flange portion 31 formed with the usual planarsurfaces 32 adapted for applying a suitable holding tool to the bodymember 24 for holding same against movement when applying the bodymember to the box 12.

The body member 24 is further formed to define an annular indentation34, forming annular ridge 35 inside same, and chamfered surfaces 36 and38 at the ends thereof.

Associated with the smaller end portion 26 of the body member 24 is aconventional box wall engaging lock nut 40, which is turned onto thebody member end portion 26 after same has been received in an opening 22of the box 12 to clamp the box wall involved against the body memberflange portion 31, and the end 28 of the body member is proportioned toreceive the end 42 of the conduit 14, which as shown in FIG. 3, abutsagainst the annular ridge 35, which thus forms a stop for the conduit.Also associated with the fitting are a contractable gland element 44,split as at 46, which in its uncontracted relation loosely fits over theexterior surface 48 of the conduit end 42, and which has a sphericallycontoured peripheral surface 50 for cooperation with chamfer 38 ofmember 24 and camming surface 52 of a clamp nut 54 that is threaded ontothe end portion 28 of the fitting body member 24. Gland element 44 inapplication is lodged in annular recess 55 defined by nut 54 between itssurface 52 and its threaded portion 57.

The fitting 10 may be employed to attach the conduit 14 to a box, suchas box 12, by first removing an appropriate knock out to open a desiredopening 22, after which the body member 24 is inserted into the opening22 and the nut turned onto the end portion 26 of the body member 24 toclamp the box wall between it and the body member flange portion 31,which is formed to define a clamping wall 56 that serves as an abutmentsurface for this purpose. The nut 54 and H the gland 44 are then appliedin that order to the end 42 of the conduit 14, and the conduit end 42 isinserted within the body member 24 to the position indicated in FIG. 3,after which the clamping nut 54 is drawn against and turned onto thebody member end portion 24 to cam the gland element 44 into clampingrelation with the conduit at its edges 58 and 59, this action closingsame firmly about the conduit to securely hold the conduit within thefitting. The gland 44 is proportioned to pass readily through thethreaded portion 57 of nut 54 into its recess 55 when the latter isbrought against the body member for application thereto.

The lock nut 40 may take the form of any conventional lock nut suitedfor the indicated purpose. Nut 54 is preferably formed from steel by asuitable screw machine operation. Gland 44 may be of any conventionalmetal or plastic element of the configuration indicated that will servethe clamping function described.

The body member 24 is preferably made by the practice of the methodillustrated in conjunction with FIGS. 4-12.

METHOD OF MAKING THE FITTING Referring now to FIGS. 4-12, the fitting10, and more specifically, the body member 24 thereof, is made inaccordance with this invention from tube stock in the form of mild steeltubing, following the procedure indicated in FIGS. 4-12, in accordancewith which a blank (FIG. 5) is formed from a length of tube stock 61 andhas indentation 34 rolled therein, after which the ends 62 and 64 of theblank 60 are deburred (FIG. 7); the blanks 60 are then consecutivelyapplied to one of a series of lower die plate structures suitablymounted on a rotating platform 68 of a dial feed type die arrangement 66to consecutively pass under a pair of upper die heads 72 and 78 (FIG. 9)which consecutively neck down the end 62 of the blank to approximatelythe area of the groove 34, as indicated at 80 of FIG. 10, and upset theblank 60 at its mid portion to define the hex surface defining flangeportion 31 (see FIG. 11).

Thereafter, the ends 62 and 64 are provided with external threads by asuitable thread rolling machine operation, after which the thus formedbody member is provided with a suitable protective coating, as byelectroplating with zinc following any suitable electroplatingprocedure.

Referring back now more specifically to FIG. 4 of the drawings, inperforming the groove forming and blank cutting steps, the end 63 of thetube stock 61 from which the blank is formed is sequentially fed througha rotating chuck structure 90, past a rotatably mounted severing orcutting blade 92 and a rotatably mounted rolling blade 94, which performthe blank rolling and cutting functions indicated. The diagrammaticillustration of FIG. 4 represents a conventional cut off machine such asthat made by Barton & Oliver, in which the blade 92 is journaled betweenthe arms 95 and 96 of a suitable head structure suitably actuated, as bya suitable hydraulic cylinder device or other conventional and suitablemeans for mechanically, hydraulically and/ or pneumatically actuatingsame to move the blade 92 toward and away from the tube stock in themanner indicated by arrow 98. Blade 92 is shaped as at 100 in accordancewith standard practices to sever a blank 60 from tube stock 61 when thetube stock 61 is rotated and blade 92 is pressed against same.

Similarly, blade 94 is journaled as at 102 between the arms 104 and 106of a suitable head structure actuated by a suitable hydraulic cylinderdevice to move toward and away from the tube stock 61 in the mannerindicated by arrow 108. Blade 94 is formed with a convexly roundedperiphery 110 proportioned to define the indentation or groove 34 whensuitably pressed against the tube stock 61 while it is rotating.

The tube stock 61 in accordance with this invention has an outerdiameter that is equivalent to the pitch diameter of the threadingapplied to the larger end portion 64 of the blank, and has an internaldiameter to closely receive and substantially complement the outerdiameter of a standard size of EMT, as indicated in FIG. 3.

In performing the operations illustrated by FIG. 4, the cut ofl? machineis operated to advance and position the end 63 of the bar stock 61 whereshown in FIG. 4 relative to chuck 90 and rotated, after which the grooveforming blade 94 is pressed against the tube stock 61 with sutficientpressure to define indentation or groove 34 as well as ridge 35circumferentially of the tube stock as same rotates, the minimuminternal diameter of which (indicated at 35 in FIG. 3) defines themaximum throat size of the fitting. The pressures required will dependupon the specific materials and sizes being processed and can bedetermined in accordance with any conventional procedure used forperforming a deformation of this type.

When the formation of groove 34 is nearing completion circumferentiallyof the tube stock, the cutting blade 92 is advanced against the tubestock 61 to sever the blank 60 from same, as at 112. After the groove 34is completed, the blade 94 is withdrawn from the tube stock, while thecutting blade 92 remains in position to complete its cutting operation.The result is the formation of the blank 60 in the form shown in FIG. 5and 6, in which the ends 62 and 64 of the blank are left with a raggedinner edge where indicated at 114, which is eliminated by the practiceof the chamfering step shown in FIG. 7.

Referring now specifically to FIG. 7, blanks 60 in the form they appearin FIGS. 5 and 6 are then consecutively chamfered as at 36 and 38 byhaving the ends 62 and 64 applied to a pair of conically shaped grindingmembers 116 and 118 rotatably mounted on their respective shafts 118 and120 that may be retracted and advanced in accordance with the respectivearrows 122 and 124.

The chamfering arrangement indicated in FIG. 7 is intended to representa suitable chamfering machine for performing same, such as that made byPines Engineering Company, in which the blanks are stacked in a chute orway and fed one by one downwardly through the machine for application tothe rotating grinding elements 116 and 118 that are automaticallyretracted and advanced to receive a blank 60 therebetween, grind theends 62 and 64 thereof to form the chamfer 36, and retract to permit thethus deburred blank to pass onto the next stage of the processingprocedure.

Turning now to the press forming die arrangement of FIGS. 9 and 12, thelower die plate structures 70 each comprise a stepped diameter mandrelpositioned within an annular holder 132 defining a bore 134 proportionto substantially complement the shank portion 136 of the mandrel 130.The mandrel 130 is shaped to define end portion 137 of a reduceddiameter which is equilavent to the inner diameter of the end 64 ofblank 60 while the bore 134 of element 132 has a diameter equivalent tothe outer diameter of the blank end 64.

The holder 132 is received within mounting element 138 that is securedto platform 68 by appropriate bolts 140. Received about the upper end ofholding element '132 is centering element 142.

One or more alignment pins 144 may be applied be tween the mountingmember 138 and the platform 68 for die alignment purposes.

Platform 68 carries plate structure 146 that supports the mandrels 130and their respective lower die plate structures 70 in the operatingposition shown in FIG. 9.

The respective blank 60 as they emerge from the chamfering procedure ofFIG. 7 are consecutively applied to the respective lower die platestructures 70 at a suitable position in advance of the position ofoperation of the upper die plate structures 72 and 78, with respect tothe circumference of the platform 68. At the operating position of upperdie plate structure 72 and 78, the platform 68 passes over a suitableabutment structure 148 that supports the platform 68 when the upper dieplate structures are applied in the manner indicated in FIG. 9.

As indicated in FIG. 9,, the individual blanks 60 are applied to therespective lower die plate structure 70 with their ends 64 received overthe end portion 137 of the rnandrels 136, and within the space definedby such end portions 137 and the respective bores 134 of holdingelements 132, the end 64 of the element 60 resting on the shoulder 150as defined by the mandrel 130 at its end portion 137.

The upper die plate structures 72 and 78 are structurally united in anysuitable manner and are connected to a common hydraulically operatedhead structure of any suitable type. The die plate structures 72 and 78are spaced apart circumferentially of the platform 68 to be aligned withtwo adjacent lower die plate structures 70 to simultaneously perform thetwo indicated press forming operations of FIG. 9.

The upper die plate structure 72 comprises a die plate 152 formed withan annular forming surface 154 and is suitably secured within holdermember 156 that is clamped to a suitable mounting plate structure 158 byclamp member 160 under the action of suitable securing bolts 162.

The forming surface 154 of die plate 152 is shaped to reduce or neckdown the end 62 of blank 60 to the configuration indicated in FIG. 10.Associated with die plate 152 is an ejector member 164 that slidablyengages within the forming surface 154 and is biased by suitablecompression spring 166 to engage its holder 168 with the back side 170of the die plate 152 in the retracted position of the die platestructure 72. Spring 166 suitably seats within a bore 172 formed in theejector member and against spring seat 176 that is suitably positionedagainst mounting plate 158.

The upper die plate structure 78 comprises a shaping die plate 180(defining a hex shaped shaping surface 181) secured to annular die platemember 182 as by appropriate screws 184, which is in turn affixed to theupper die plate mounting member 186 by appropriate bolts 188. Fixedwithin the die plate member 182 is annular guide element 190 defining abore 192 having a diameter equivalent to the outer diameter of thenecked down surface 194' of blank end 62. Mounted within the bore 192 ofmember 190 is thrust member 196 having an annular stem portion 198, theouter diameter of which is substantially equivalent to the diameter ofbore 192, and which slidably receives the head portion 200 of a mandrel202 that is fixedly mounted within mounting structure 186, as bysuitable set screws 204.

Die structure 78 includes one or more stripping pins 206 that areoperated to engage the thrust member 196, and that are simultaneouslythrust downwardly on withdrawal of the die plate structure 78 to ejectthe upset blank from guide member 190 after the press forming action ofthe upper die plate structure 78 has been completed.

As indicated, the upper die plate structures 72 and 78 are united in anysuitable manner to form a composite upper die plate structure that hasbeen generally designated as 210, which in turn is afiixed to theoperating head of a suitable hydraulic cylinder device for forcing thecomposite die plate structure 210 downwardly against the lower die platestructures 70 positioned under same with sufficient force to perform thepress forming operations indicated.

In operation, the dial feed arrangement of FIGS. 9 and 12 contemplatesthat the individual blanks 60 will be applied in a consecutive manner ata station, such as that indicated at 12 of FIG. 12, with the platform 68being rotated in an intermittent manner to a press forming station atwhich the composite upper die head structure 210 operates, such as whereindicated at 214 in FIG. 12. As a lower die plate structure 70 carryinga blank 60 in the manner indicated in FIG. 9 reaches the first position216 of station 214, and platform 68 is at rest momentarily to hold theindicated lower die plate structure 70 in that position, the compositeupper die plate structure 10 is lowered to bring the forming member 152into forming engagement with the end 62 of blank 60 in the mannerindicated in FIG. 9 to shape the blank 60 as indicated in FIG. 10,whereupon the head structure 210 is withdrawn, with ejector member 164under the action of spring acting to insure that the die plate structure70 passes freely from the blank .60 without disturbing the position ofsame.

The platform 68 is then actuated to move the lower die plate structure70 in question to position 218 of station 214, this action alsopositioning the next succeeding lower die plate structure at position216. When movement of platform 68 is again momentarily ceased, thecomposite die plate structure 210 is lowered to perform the indicatedpress forming operations on the blank 60 being processed; in the case ofthe upper die plate structure 78, the necked down end portion 62 isreceived within the bore 192 of holding member 190, and as the die platestructure 78 continues to lower, the terminal end portion 220 of theblank is engaged by the annular stern portion 198 of thrust member 196,which presses the blank end portion 62 downwardly, upsetting same as at222 outwardly thereof into engagement with the hex configuration formingsurface 181 of shaping member 180. The parts of the upper die platestructure 78 are so proportioned that when shaping plate member engagesthe lower die plate structure 70 beneath same, the upsetting deformationof the blank indicated in FIG. 9 has been completed to define thefitting blank hex shaped portion 30.

On withdrawal of the composite head structure 210, stripping pins 206are operated by suitable hydraulic mechanisms or the like to forcethrust member 196 downwardly and effect ejection of the blank 60 fromholding member and shaping member 180. The ejected blanks are picked upin any suitable manner for further processmg.

Platform 68 may be automatically operated in any suitable manner tointermittently rotate same in the time sequence indicated to permitmanual application of the individual blanks 60 at the station 212 andthe press forming functions that are indicated for the positions 216 and218 of station 214.

The blanks when ejected from die plate structure 78 having theconfiguration indicated in FIG. 11 and at this point the ends 62 and 64are threaded by a suitable rolling machine operation, a Reed threadrolling machine being adequate for this purpose. The ends 62 and 64 ofthe blank 60 may be threaded simultaneously or sequentially in anydesired order, which provides the fitting body member indicated in FIGS.1-3, that is then suitably coated with a protective finish, as alreadyindicated.

As previously indicated, the blank 10 is formed from tube stock havingan outer diameter that is the same as the pitch diameter of the threadsat the blank end 64. The pitch diameter referred to is indicated by thedimension A of FIG. 3 relative to the major and minor diameters of thethreading of blank end 64, indicated by dimensions B and C respectively;thus, if circles were drawn with the dimensions A, B and C, the circledefined by the dimension A would be half way between the circles definedby the dimensions B and C.

The significance of this is that the formation of the threading byrolling presses the material of the blanks 60 radially outwardly to formthe major diameter of the threads, with the minor diameter of thethreads being defined by indentations formed in the blank. Thus theexternal surface of the blank is not cut away to define the screwthreads, making it possible to use tube stock of minimum OD size andthickness. The thread rolling machine procedure avoids cutting and thussaves material; further, it is a faster way of forming threading thancutting type threading procedures. In any event, this invention permitsthe fitting body member 24 to be formed from tube stock having an OD nolarger than the pitch diameter of the threading for the larger end 64 ofthe blank.

In a commercial form, the pitch at the blank end 62 is 14 threads perinch while at the end 64 the pitch is 18 threads per inch. The fillingis made in sizes ranging from one half inch to two inches diameter (thepitch diameter of the blank end 64) in one half inch steps forapplication to conduit of corresponding size.

The compression fitting is completed by the application thereto of thenuts 40 and 54 and gland 50 in the manner previously indicated.

It will therefore be seen that this invention has provided a method ofmaking compression fittings and a compression fitting resulting from thepractice of the same that significantly reduces the cost of labor andhardware to perform the method. The method steps indicated may obviouslybe performed by comparatively unskilled help, as compared to complex diecasting and deep drawing apparatus. The only material wasted frompractice of this method is that removed by the cutting of the blank 60from the tube stock and the chamfering at 36 and 38 in deburring theblank.

The foregoing description and the drawings are given merely to explainand illustrate the invention and the invention is not to be limitedthereto, except insofar as the appended claims are so limited, sincethose skilled in the art who have the disclosure before them will beable to make modifications and variations therein without departing fromthe scope of the invention.

We claim:

1. The method of making a body member for compression fittings of thetype adapted to connect conduit to outlet boxes and the like, saidmethod comprising:

forming a blank from one end of mild steel tubing having an indentationformed in same about the blanks periphery and ositioned inwardly of oneend thereof approximately one third the length of the blank, deburingthe ends of the blank,

necking down said one end of said blank to approximately saidindentation,

upsetting said blank intermediate the ends thereof and adjacent saidindentation to define a hex shaped peripheral portion about said blank,

and rolling threading into said ends of said blank.

2. The method set forth in claim 1 wherein:

8 the tubing has an outer diameter equivalent to the pitch diameter ofthe threading of the other end of said blank.

3. The method set forth in claim 1 including electroplating said blankto complete same.

4. The method of making a body member for compression fittings of thetype adapted to connect conduit to outlet boxes and the like, saidmethod comprising:

taking a length of tubing and rolling in one end thereof at a pointspaced from the terminous of said end thereof an indentationproportioned to define the throat of the fitting,

severing a blank from said tubing one end proportioned to include saidindentation spaced from said ends of said blank but positioned adjacentone of said ends thereof,

deburring the ends of the blank,

upsetting said blank intermediate the ends thereof and between saidindentation and the other end thereof to define a hex shaped peripheralportion intermediate the ends of said blank,

rolling threading into the external surfaces of said ends of said blank,

and coating said blank with corrosion resisting material.

5. The method set forth in claim 4 wherein:

the tubing has an outer diameter equivalent to the pitch diameter of thethreading of the other end of said blank.

6. The mehod of making a compression fitting of the type adapted toconnect conduit to outlet boxes and the like, said method comprising:

taking a length of tubing and rolling in one end thereof at a pointspaced from the terminous of said end thereof an indentationproportioned to define the throat of the fitting,

severing a blank from said tubing one end proportioned to include saidindentation spaced from said ends of said blank but positioned adjacentone of said ends thereof,

deburring the ends of the blank,

upsetting said blank intermediate the ends thereof and between saidindentation and the other end thereof to define a hex shaped peripheralportion intermediate the ends of said blank,

rolling threading into the external surfaces of said ends of said blankto complete the formation of the body member of said fitting,

coating said body member with corrosion resisting material,

and applying a lock nut to said one end of said body member and a clampnut and cooperating gland to the other end thereof.

References Cited UNITED STATES PATENTS 2,053,808 9/1936 Young 29 157 X2,089,784 8/1937 Cornell 29 157 X 2,630,339 3/1953 Appleton 285158 JOHNF. CAMPBELL, Primary Examiner D. M. HEIST, Assistant Examiner U.S. Cl.X.R.

UNZTED STATES PAQENT U1 FZ'CE CERTIFICATE OF QGRRECTEON Patent Na.3,616,522 Dated November 2, i971 Inveuwfl nmman H. Rudolnh et a1 It; iscertified that error apgaeam in the abava-identified patent and thatsaid Letters Eaten wca wan-sated m shown balms;

CClumn 1, line 2% after blank is insevt mafia from mild steel tubing fedthrough a cut .off machine in which the,

indentation is r'olle'd into the tubing and the blank is Column 2, line2 for of read by Column 7, line 59, for debur'ing" mad debut-ring Column8, line 29, for "me'l rod", read method Sign ed and sealed this 25th dayof A r-11 19,72.

(SEAL) I r v tcest:

, EIJwARD M.FLETCHER',J'RV \RVOBERT GQ'TTSGHALK AtT es tingOffi'ger' V vCbmmi s'si oner of Patents l o I

